1. Field of the Invention
The invention relates to a method and apparatus for decontaminating oily mixed waste fluid containing water and soil polluted with hydrocarbons. This invention proposes a treatment method where the separated hydrocarbons and treated water are used in the process of treating the soil (also generally referred to as media).
2. Description of the Related Art
Many sites around the world are polluted in such a way that both the soil and any adjacent water are both contaminated by hydrocarbons from the same source. Systems previously dealt with this problem by using separate facilities for decontamination, one for soil decontamination, another facility for water decontamination. There are also a number of existing soil treatment facilities but they have no ability to treat the waste fluid in conjunction with the soil treatment process.
Jaisinghani (U.S. Pat. No. 4,315,822) discloses a system for the separation of oil and water from bilge water. Jaisinghani addressed the problem of inadvertent and undesired emulsification of the oil and water when the bilge was pumped out. Conventional pumping means used high pressure pumps as a matter of course, with the emulsification of the oil and water being the result. To remedy this, Jaisinghani chose to accomplish all the pumping within the system by one and only one low pressure, low emulsification pump for all of the various pumping jobs in the oil/water separation process.
A regenerative filter is used within the system disclosed by Jaisinghani to separate the oil from the water in the bilge. This regenerative filter required occasional backwashing to regenerate it. There was no provision for doing anything with the used backwash water other than to send it to a backwash water outlet as untreated waste.
Another shortcoming of the approach used by Jaisinghani is that by using only one pump type, the designer is forced to pick a pump that is only optimal for one or two of the many jobs required from the pump. For the other pumping jobs within the system, such as pumping the clarified water to its outlet, a low pressure and low emulsification pump is a less desirable pump for the job. Also, with only one pump, the system throughput is severely limited since only one step within the process could be done at any given time.
Torline et al. (U.S. Pat. No. 5,227,071) disclose a water decontamination system. This oil/water separation system has four or five stages that include a coalescer, an ultra filtration stage, an activated carbon filter, a cation exchange column, and an optional gravity separation stage and/or a clarification stage. The goal of Torline et al. was to treat contaminated mixed waste fluids, including those contaminated with heavy metals, to the point that they met the environmental regulations for discharge of the decontaminated water into surface waters.
A disadvantage to the system disclosed by Torline et al. is that there are a number of outflow products that require further treatment by other systems not mentioned in the disclosure before they can be safely disposed. These other outflow products include used backwash water from the activated carbon filter, heavy metal contaminated used backwash water from the cation exchange tower, and unprocessed sludge from the oil/water separator.
Another disadvantage to the system disclosed by Torline et al. is the inclusion of ion exchange, activated charcoal, and membrane filtration sub-systems. All of these systems have cost, maintenance, backwashing, and repair needs which require considerable effort and expense. The complexity of the system disclosed by Torline et al. was needed to have the treated water produced meet very strict standards so that it may be discharged directly into surface water. This incurs considerable complexity of design, expense, and the need to deal with an additional effluent outflow that itself requires further treatment by another decontamination system.
Kitko (U.S. Pat. No. 5,350,527) discloses a system for treating contaminated water to the point that it can be discharged into surface water. This system is intended for use in an industrial environment and includes a number of stages. In this system there are two stages of membrane filtration with successively smaller pore sizes followed by a heavy oil gravity separator, settling tanks, a light oil coalescer, an even finer pore size membrane filter, and finally an activated charcoal filter.
An alleged advantage to this system disclosed by Kitko is that the water treated could be continuously re-cycled in a closed loop. Despite this, there is no specific mention of how to deal with the contaminants that are entrapped by the various elements within the system. When this system is backwashed or cleaned, the resultant effluent is removed from the site and dealt with as contaminated waste, which incurs additional effort and expense. Another disadvantage to this system, like Jaisinghani and Torline et al., is the inclusion of a number of sub-systems such as an activated charcoal filter and a number of membrane filters that incur considerable effort and expense for their installation, maintenance, and repair.
Ballard et al. (U.S. Pat. No. 5,288,330) disclose a means and apparatus that decontaminates particulate matter, including sand, gravel, and soil. This is done in this system by washing the particulate matter to be decontaminated with heated water. This used heated wash water is then treated and reused within the process.
It is stated in the Ballard et al. disclosure that the wash water is to be heated to a temperature greater than the melting point of at least some of the contaminants. Also, if necessary for a specific pollutant being treated, acetic acid could be added to the heated wash water to dissolve heavy metals in the material being decontaminated. In this system the used wash water is purified by two gravity separation stages, activated charcoal filtration, ion exchange filtration, and a two stage membrane filtration with each having successively smaller pore sizes. After all of this filtration, the water is reused as wash water again.
There are a number of disadvantages and shortcomings with the system disclosed by Ballard et al. The temperature of the heated water used to melt contaminants is limited by its boiling point which would also limit its effectiveness. Also, the contaminants that are removed from the particulate matter being treated by the heated wash water are deposited into the various separation and filtration means. All of these sub-systems require their own cleaning by backwashing or other means, and the effluent from cleaning them produces contaminated waste that requires the additional effort and expense of treating them at another facility.
As in the disclosure by Torline et al., Ballard et al. also has number of sub-systems requiring maintenance, backwashing, and repair, also incurring additional effort and expense.
Another system to decontaminate soil is disclosed by Guymon (U.S. Pat. No. 5,252,138). This method of treating contaminated soil, like that disclosed by Ballard et al. involves washing the contaminated soil with water. Unlike the Ballard et al. disclosure however, Guymon proposes the use of a non-ionic surfactant, a type of detergent, to remove hydrocarbon contaminants from the soil being treated. Guymon discloses the use of a specific group of surfactants to enable the wash water to dislodge oils from the soil.
Guymon makes no attempt to deal with the mechanics involved in treating the soil or cleaning the wash water used to treat the soil. Also, the issue of how to handle or dispose the recovered oily contaminants is not considered, leaving the operator with the effort and expense of treating these contaminants by other means.
A system to decontaminate sand or soil polluted by hydrocarbons is disclosed by Toor (U.S. Pat. No. 5,344,255). Like the Guymon disclosure, Toor uses a non-ionic surfactant, a type of detergent, in a water solution to wash the soil and then decontaminates the wash water so that it can be reused continuously. This system has an initial separation stage, at least one washing phase, at least one rinsing phase, an oil/water separator of the coalescer type, and a flocculation tank. Other embodiments disclosed by Toor also include one or more of the previously mentioned stages as well as one or more hydro-cyclones to remove particulate matter from the recycled wash water.
For all of its complexity, the Toor system does not provide for the disposal of the oil recovered or for the handling and disposal of contaminated fines and silt. These contaminated outputs must be processed by other means not included in this disclosure. This system also incurs additional expense because it continuously consumes detergent and flocculant that cannot be recycled or reused during operation.
Lebowitz (U.S. Pat. No. 5,461,186) discloses mixing of coal and water into the contaminated soil and then cooking this mixture to remove volatile contaminants. This step is followed by screening, dewatering, and finally, burning the mixture.
The mixture is heated and agitated while it is still wet, which limits the temperature in this step of the process to the boiling point of the water. This is not hot enough to volatilize all the contaminant hydrocarbons, but these other not yet volatilized hydrocarbons are consumed in the final step when the mixture is burned.
Burning coal as a decontamination strategy leaves the ecological clean-up problem of the entire coal burning process. Also there is no provision mentioned for treating the volatilized hydrocarbons from the hot water wash within the process. This contaminated waste must be treated and disposed of by some other means.
Nowhere in the related art is a system that fully integrates the two processes, one decontaminating soil and the other decontaminating mixed oily waste water, within a single processing facility in such a way that there is no contaminated output whatever.